Utility vehicle having hydrostatic drive

ABSTRACT

A utility vehicle is disclosed within. The utility vehicle comprises a front axle, a pair of rear axle shafts, a seat for at least two occupants positioned between the front axle and the rear axle shafts, a load bed positioned over the rear axle shafts, a prime mover with a prime mover output shaft with a pulley attached to the end of the prime mover output shaft. Further, the vehicle has a hydraulic drive system that has a hydraulic pump driven by a pump input shaft, a hydraulic motor located within a common housing with the hydraulic pump, and gears and a differential located in the common housing with the hydraulic pump and the hydraulic motor. The prime mover output shaft and the pump input shaft are parallel to the front axle and the rear axle shafts.

This application is a divisional of U.S. patent application Ser. No.10/314,814, filed on Dec. 9, 2002, now U.S. Pat. No. 6,860,358 whichclaims the benefit of U.S. Provisional Patent Application Ser. No.60/416,027, filed on Oct. 4, 2002, both of which are incorporated hereinby reference in their entirety.

BACKGROUND OF THE INVENTION

This invention relates to hydrostatic transmissions (HSTs) andintegrated hydrostatic transaxles (IHTs) where the HST is in a commonhousing with output gearing, a differential, output axles and the like.The general design of an IHT is known, and is disclosed in U.S. Pat.Nos. 5,314,387 and 6,185,936, the terms of which are incorporated hereinin their entirety. Such IHTs are generally used with lawn and gardentractors and similar low speed vehicles.

Hydrostatic technology has also been used in higher speed vehicles suchas utility vehicles, but such vehicles generally use a system having aplurality of hydrostatic pumps connected to a plurality of wheel motorseach driving an independent wheel. Furthermore, while such pumps andwheel motors have been used, the most typical method of propulsion insuch utility vehicles uses a variable sheave to change the speed intothe transmission. The former system is disadvantageous because of thecomplex valves and controls involved in controlling flow to the wheelmotors. The latter system suffers from inconsistent transmission oftorque, high maintenance costs, and lower performance under some wetconditions.

SUMMARY OF THE INVENTION

In order to overcome the disadvantages listed above, it is an object ofthis invention to use a hydrostatic transmission or integratedhydrostatic transaxle driving a pair of rear axles of a utility vehicle,where the HST or IHT is located under the utility bed of the vehicle,and the vehicle has a mid-mounted engine located between the front andrear axles of the vehicle.

In one embodiment, a BDU style hydrostatic transmission is mounted to agearbox to form a unitary transmission, which is then secured to therear axle of the utility vehicle. Such a transmission has a pump andmotor mounted in parallel in a common housing. In yet anotherembodiment, a hydraulic pump drives a hydraulic motor which then drivesa gear reduction in a utility vehicle. Additional embodiments aredescribed in detail herein.

A better understanding of the objects, advantages, features, propertiesand relationships of the invention will be obtained from the followingdetailed description and accompanying drawings which set forth anillustrative embodiment and is indicative of the various ways in whichthe principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom schematic plan view of a vehicle incorporating afirst embodiment of this invention.

FIG. 2 is a bottom schematic plan view of a vehicle incorporating asecond embodiment of this invention.

FIG. 3 is a bottom, partially-schematic plan view of a vehicleincorporating another embodiment of this invention.

FIG. 4 is a top, partially-schematic plan view of the vehicle shown inFIG. 3, with certain components shown in outline for clarity.

FIG. 5 is a schematic plan view of the transmission and other drivecomponents of the vehicle shown in FIG. 3.

FIG. 6 is a side, partially-schematic view of a vehicle in accordancewith a further embodiment of this invention.

FIG. 7 is a schematic plan view of the transmission and other drivecomponents of the vehicle shown in FIG. 6.

FIG. 8 is a side, partially-schematic view of a vehicle in accordancewith another embodiment of this invention.

FIG. 9 is a schematic plan view of the transmission and other drivecomponents of the vehicle shown in FIG. 8.

FIG. 10 is a bottom schematic plan view of a further embodiment of thisinvention.

FIG. 11 is a side schematic view of the vehicle shown in FIG. 10.

FIG. 12 is a bottom, partially-schematic plan view of a vehicleincorporating a further embodiment of this invention.

FIG. 13 is a side, partially-schematic view of a vehicle incorporating afurther embodiment of this invention.

FIG. 14 is a bottom, partially-schematic plan view of a vehicleincorporating another embodiment of this invention.

DETAILED DESCRIPTION OF THE DRAWINGS

A first embodiment of this invention is shown schematically in FIG. 1,where vehicle 10 has a frame 12 and a front axle 15, rear axles 17 andengine 14 mounted thereon. It is intended that vehicle 10 be a utilityvehicle with a working bed 48, as shown, for example, in FIGS. 4 and 6;the manner in which such elements as axles 15 and 17 or engine 14 aresecured to frame 12 are not critical to the invention and will be knownto one of skill in the art. A plurality of vehicle wheels 13 are securedat the ends of axles 15 and 17. A variety of different embodiments aredisclosed herein. As shown most clearly in, e.g., FIGS. 6 and 14, it isintended that the vehicle 50 or 90 have a seat 39 with space for atleast two people to ride side-by-side thereon and a working bed 48 orsimilar structure extending to the rear of the vehicle and over the rearaxles 37 or 89. The benefits of this arrangement are an improvedrelationship of the engine with respect to the transaxle, and inparticular with regard to the flexibility of the application. Thearrangement taught herein gives the user the ability to select variousinput locations to correspond to the output locations of differentengine configurations.

An integrated hydrostatic transaxle (IHT) 16 is also secured to frame 12in a known manner and has an input shaft 21 extending out therefrom; inthe embodiment shown in FIG. 1, input shaft 21 is coaxial with enginedrive shaft 18 and is coupled via connecting shaft 20 and couplers 19.

FIG. 2 shows another embodiment of the invention. In the alternativeembodiment disclosed herein, like numerals represent structure identicalor substantially identical to that described before. In this view,vehicle 30 has engine 24 with a drive shaft 27 extending out one sidethereof and parallel to axles 15 and 17. Engine drive shaft 27, whichmay also be referred to as an output shaft, is engaged via pulley 29Band belt 28 to pulley 29A and input shaft 31 which drives IHT 26.

The IHTs 16 and 26 may have a pump and motor parallel to one another,such as in U.S. Pat. No. 5,392,670, or these units may be at rightangles to one another such as in Pat. No. 5,314,387. Input shafts 21 and31 may be directly coupled to the hydraulic pump (not shown) or it maybe coupled to a separate pump input shaft through a bevel gear orsimilar arrangement.

In the alternative embodiment depicted in FIGS. 3–5, vehicle 40 hasengine 24 mounted thereon, and a connection to the transmission similarto that shown in FIG. 2. The transmission in this embodiment iscomprised of a bantam duty hydrostatic transmission 35 such as aHydro-Gear BDU-10, coupled to gear box 36. In this embodiment, gear box36 is comprised of two casing halves 38A and 38B, joined together alonga vertical split line 41 that is perpendicular to the longitudinal axesof axles 37 and 15. A pair of rear axles 37 are driven by gear box 36and extend from the respective casing halves 38A and 38B to drive wheels13. In this embodiment, pump input shaft 31 is directly engaged tohydraulic pump 33.

Pump 33 and motor 43 are mounted inside the casing of HST 35, which issecured to gear box 36, and are connected through porting 42 or anotherhydraulic connection means. Motor shaft 45 is directly coupled to motor43 and extends out of HST 35 into gear box 36, where it engages geartrain 46, which comprises a plurality of gears 46A to 46F and varioustransfer shafts 44A and 44B. Axles 37 are driven by gear train 46through differential 47. A charge pump or auxiliary pump 34 mayoptionally be used to increase the hydraulic pressure in the system orto provide hydraulic fluid for power steering, raising bed 48, or otherapplications as needed; in this embodiment pump 34 is powered by pumpinput shaft 31.

In the embodiment depicted in FIGS. 6 and 7 pump input shaft 31 extendsupwards from HST 35 and parallel to engine drive shaft 27. Pulleys 29Aand 29B and belt 28 connect drive shaft 27 to input shaft 31. As in theembodiment described above, a pump 33 is engaged to motor 43 throughporting 42, and motor shaft 45 extends out of HST 35 and into gear box36, where it drives a gear train 46. The key distinction in the geartrain arrangement disclosed in this embodiment is the use of bevel gears32A and 32B to create a 90° turn of the rotational force from motorshaft 45. This arrangement gives the user flexibility in deciding how tomount HST 35 with respect to gear box 36.

FIG. 8 depicts a similar vehicle 60, where the key difference from thatshown in FIG. 6 is the use of connecting shaft 49 and couplers 51 totransfer rotational power from engine drive shaft 27 to HST input shaft31, and input shaft 31 is mounted coaxially with drive shaft 27 andperpendicular to axles 37. Note that connecting shaft 49 is optional anddrive shaft 27 may be connected to input shaft 31 by means of a coupler51, which may be a universal joint coupler for flexibility. Motor shaft45 is mounted perpendicular to axles 37 and along the longitudinal axisof the vehicle, as shown most clearly in FIG. 9. Motor shaft 45 isengaged to gear train 46 through bevel gears 32A and 32B. Charge orauxiliary pump 34 is again optionally used and may be driven by inputshaft 31.

FIGS. 10 and 11 depict a similar utility vehicle 60, where engine 58 isconnected to HST 57 through pulleys 61 and 54 in a manner similar tothat described above. Pump input shaft 63 is driven by pulley 54 anddrives the hydraulic pump, which is not shown in this embodiment. Thehydraulic motor output shaft 65 drives pulley 55, and the rotationaloutput of HST 57 is transferred through pulley 55 to pulley 53 and thento gear box input shaft 52 to drive gear box 56, which in turn isengaged to and drives output axles 59. As shown most clearly in FIG. 11,idler pulleys 62 may be used to maintain belt wrap and tension. Pumpinput shaft 63 and motor output shaft 65 may be located in a plane whichis parallel to, e.g., the longitudinal axis of rear axle 59, and pumpinput shaft 63 is located above motor output shaft 65 with respect tothe ground.

FIG. 12 shows an alternative embodiment of vehicle 70, where engine 58is connected to hydraulic pump 66 through pulleys 61 and 67 in a mannersimilar to that described above. In order to increase the flexibility,this embodiment does not use a unitary HST such as is shown in, e.g.,FIGS. 3, 4, 6 and 8 above, but rather uses a separate hydraulic pump 66and hydraulic motor 69 connected through high pressure hoses 71. Motor69 is then mounted on gear box 68.

FIG. 13 depicts another embodiment where engine 77 has an output shaft79 extending downwardly therefrom, and perpendicular to the longitudinalaxis of the vehicle 80. HST 76 is mounted to gear box 75 in such amanner that input shaft 74 also extends downwardly therefrom andparallel to engine shaft 79, so that the two shafts can be connectedthough pulleys 88A and 88B. This embodiment affords additionalflexibility in the mounting of the primary components of the vehicle.

FIG. 14 shows another embodiment showing vehicle 90, where separate pump81 and motor 84 are connected via hoses 85. Pump 81 is mounted so thatpump input shaft 64 is parallel to engine output shaft 27 of engine 24,and both are parallel to axles 15 and 89. A separate reservoir 82 andoptional oil cooler 83 are also connected to this hydraulic circuitthrough hoses 85. Motor 84 is secured to gear box 86 through pulleys 87Aand 87B. While all the hoses in this figure are all identified as hose85, it will be appreciated by those of ordinary skill in the art thatthe specifications of each hose will be dependent on where they areused. For example, the hoses between the pump 81 and motor 84 will becapable of carrying high pressure hydraulic fluid, and the hose from theoil cooler 83 to the pump 81 will carry oil that may be at less thanatmospheric pressure.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof.

1. A utility vehicle comprising: a front axle; a pair of rear axleshafts; a seat for at least two occupants positioned between the frontaxle and the rear axle shafts; a load bed positioned over the rear axleshafts; a prime mover located between the front axle and the rear axleshafts and at least partially positioned below the seat, the prime moverhaving a prime mover output shaft that extends from the prime movergenerally perpendicular to the longitudinal direction of the vehicle anda pulley attached to the end of the prime mover output shaft; and ahydraulic drive system drivingly coupled to the rear axle shafts anddriven by the prime mover by a belt and pulley system, wherein thehydraulic drive system comprises: a hydraulic pump driven by a pumpinput shaft, the pump input shaft comprising a pulley; a hydraulic motorlocated within a common housing with the hydraulic pump, andhydraulically connected to the hydraulic pump and driving a motor outputshaft; and gears and a differential located in the common housing withthe hydraulic pump and the hydraulic motor; wherein the prime moveroutput shaft and the pump input shaft are parallel to the front axle andthe rear axle shafts.
 2. A vehicle comprising: a front axle; a hydraulicdrive system, comprising: a hydraulic pump driven by a pump input shaftwith a pump input pulley; a hydraulic motor hydraulically driven by thehydraulic pump and driving a motor output shaft; a plurality of gearsdriven by the motor output shaft; a differential driven by the pluralityof gears; and a pair of rear axle shafts driven by the differential; agenerally unenclosed seat for side-by-side seating of at least twooccupants positioned between the front axle and the rear axle shafts; aprime mover located between the front axle and the rear axle shafts andat least partially positioned below the seat and having a prime moveroutput shaft with a prime mover output pulley attached to the end of theprime mover output shaft; a load bed extending from the seat toward therear axle shafts; a belt coupling the pump input pulley with the primemover output pulley; and wherein the front axle, the rear axle shafts,the pump input shaft and the motor output shaft are generally parallel.3. A vehicle comprising: a front axle; a pair of rear axle shafts; agenerally unenclosed seat with side-by-side seating for at least twooccupants, the generally unenclosed seat positioned between the frontaxle and the rear axle shafts; a prime mover positioned generally at thecenter of the vehicle, the prime mover having a prime mover outputshaft; a bed extending from an area over the prime mover to the rearaxle shafts; a hydraulic drive system having a pump input shaft and amotor output shaft, the hydraulic drive system drivingly coupled to therear axle shafts and driven by the prime mover through a belt, whereinthe belt couples the prime mover output shaft with the input shaft; andwherein the prime mover output shaft, pump input shaft, the front axleand the rear axle shafts are parallel.
 4. A utility vehicle comprising:a front axle; a pair of rear axle shafts; a seat for at least twooccupants positioned between the front axle and the rear axle shafts; aload bed positioned over the rear axle shafts; a prime mover locatedbetween the front axle and the rear axle shafts and at least partiallypositioned below the seat, the prime mover having a prime mover outputshaft that extends from the prime mover generally perpendicular to thelongitudinal direction of the vehicle and a pulley attached to the endof the prime mover output shaft; and a hydraulic drive system drivinglycoupled to the rear axle shafts and driven by the prime mover by a beltand pulley system, wherein the hydraulic drive system comprises: ahydraulic pump driven by a pump input shaft, the pump input shaftcomprising a pulley; and a hydraulic motor located within a commonhousing with the hydraulic pump, and hydraulically connected to thehydraulic pump and driving a motor output shaft, wherein the motoroutput shaft is perpendicular to the pump input shaft.
 5. The utilityvehicle of claim 4, the hydraulic drive system further comprises gearsand a differential located in the common housing with the hydraulic pumpand the hydraulic motor.
 6. The utility vehicle of claim 4, wherein theprime mover output shaft extends from the prime mover away from thevehicle.
 7. The utility vehicle of claim 4, wherein the prime moveroutput shaft extends from the prime mover toward the vehicle.
 8. Theutility vehicle of claim 4, wherein the hydraulic pump input shaftextends from the hydraulic pump away from the vehicle.
 9. The utilityvehicle of claim 4, wherein the hydraulic pump input shaft extends fromthe hydraulic pump toward the vehicle.
 10. The utility vehicle of claim4, wherein the common housing may be positioned in at least twoorientations with respect to a gear box containing gears driven by thehydraulic motor.
 11. A vehicle comprising: a front axle; a hydraulicdrive system comprising a hydraulic pump driven by a pump input shaftwith a pump input pulley, a hydraulic motor hydraulically driven by thehydraulic pump and driving a motor output shaft, a plurality of gearsdriven by the motor output shaft, a differential driven by the pluralityof gears, and a pair of rear axle shafts driven by the differential; agenerally unenclosed seat for side-by-side seating of at least twooccupants positioned between the front axle and the rear axle shafts; aprime mover located between the front axle and the rear axle shafts andat least partially positioned below the seat and having a prime moveroutput shaft with a prime mover output pulley attached to the end of theprime mover output shaft; a load bed extending from the seat toward therear axle shafts; and a belt coupling the pump input pulley with theprime mover output pulley; wherein the motor output shaft is generallyperpendicular to the prime mover output shaft, the pump input shaft, thefront axle and the rear axle shafts.
 12. The vehicle of claim 11,wherein the hydraulic pump and the hydraulic motor are located within afirst housing attached to a second housing containing the plurality ofgears and the differential.
 13. The vehicle of claim 11, wherein thehydraulic drive system is an integrated hydrostatic transaxle.
 14. Avehicle comprising: a front axle; a pair of rear axle shafts; agenerally unenclosed seat with side-by-side seating for at least twooccupants, the generally unenclosed seat positioned between the frontaxle and the rear axle shafts; a prime mover positioned generally at thecenter of the vehicle, the prime mover having a prime mover outputshaft; a bed extending from an area over the prime mover to the rearaxle shafts; and a hydraulic drive system having a pump input shaft anda motor output shaft, the hydraulic drive system drivingly coupled tothe rear axle shafts and driven by the prime mover through a belt;wherein the motor output shaft is perpendicular to the front axle, therear axle shafts, the pump input shaft and the prime mover outputshafts.
 15. The vehicle of claim 14, wherein the hydraulic drive systemcomprises a housing containing a hydraulic pump driven by the pump inputshaft, and a hydraulic motor, hydraulically connected to the hydraulicpump and driving the motor output shaft.
 16. The vehicle of claim 15,wherein the housing further contains a plurality of gears driven by themotor output shaft.
 17. The vehicle of claim 16, wherein the housingfurther contains a differential driven by the plurality of gears anddrivingly engaged to the rear axle shafts.